Dielectric barrier discharge lamps with protective coatings are known in the art. WO2006072893, for instance, describes a system incorporating a DBD lamp, a dielectric barrier discharge (DBD-) lamp, and a phosphor coating for use as luminescent coating in a dielectric barrier discharge (DBD-) lamp, especially in a mercury-free DBD-lamp, comprising several phosphor grains together forming a luminescent coating layer for converting a primary discharge radiation into a wanted radiation, whereby the phosphor coating comprises a protective coating layer at least partly surrounding the luminescent coating layer for minimizing degradation of the luminescent coating layer during use in a DBD-lamp.
Further, also coatings on luminescent material particles are known in the art. U.S. Pat. No. 5,051,277 for instance describes a method of making a bi-layer coating on phosphor particles. The first layer surrounding the phosphor is silica. The second layer surrounding the phosphor is alumina. The bi-layer phosphor is considered to be useful in fluorescent lamps providing improved maintenance and brightness. The bi-layer phosphor can also be used in high color rendition lamps employing blends of phosphors.